1. Field of the Invention
This invention relates to an apparatus used to measure and size human feet as a guide to fitting mass produced footwear. More specifically, it applies to electronic, solid-state digital design intended primarily for self-service retail applications.
2. Prior Art
With the inception of mass produced footwear, it was recognized that an efficient means by which to match the individual foot to the closest available standard last was required to simplify selection and insure proper fit. This resulted in the manufacture and patenting of a wide variety of devices ranging from simple metering sticks to assorted electronic, mechanical, electromechanical designs and even highly complex three-dimensional imaging systems. Such methods are well documented as cited in U.S. Pat. Nos. 4,294,014, 5,323,650 and 5,123,169.
However, before evaluating such designs, a brief comment regarding the purpose and practicality of such a mechanism may help clarify the ensuing analysis. It should be noted that shoe sizing is not an exact science, primarily for two reasons. First, it is highly subjective in nature leading various manufacturers to place emphasis on different anatomical measurements such as ball girth, instep, waist and length in the last development. This is most evident by the fact that, while US manufacturers have more than ten designations governing width, European makers use length only. Second, although numerous sizing scales have been developed, no industry standard yet exists. Due to traditional practice and the competitive nature of last development and protection, most manufacturers continue to use their own sizing scales. This has resulted in the development of sizing methods with inconsistencies which prevent the development of a universal standard or even a consistent set of conversion factors long sought by international footwear distributors. What this means to the individual is that any `size` provided by such a measuring device can be best interpreted as only a rough estimate or starting point to selection of mass produced footwear of varying manufacturer and local.
Regardless of the method used, in order to detect the pattern presented by a foot, some form of transducing medium is required. This is generally handled in one of two ways: (1) using one or more radiating transducers/transceivers which move physically across the sensing surface under control of synchronized servos or motors as realized in designs of U.S. Pat. No. 3,328,882 or using an array of numerous discrete stationary elements distributed the sensing plane as is realized in U.S. Pat. Nos. 4,294,014 and 5,323,650.
The first has the advantages of using a minimal number of transducers and associated control circuitry and theoretically infinite resolution. The disadvantages are the use of mechanical or electromechanical components which generally consume more power, are bulkier, less reliable and relatively more difficult to operate. The second has the advantages of simplified operation, compact design and enhanced reliability afforded by solid-state construction and disadvantages including a greater part count, use of discrete transducer elements, more complex control circuitry, finite resolution and more sophisticated manufacturing techniques.
The invention presented here is superior to previous designs because of its enhanced practicality achieved by using a distributed transducing medium.